1. Field of the Invention
The present invention relates to a projector and a method of projecting a projection image.
2. Description of the Related Art
A projector is an apparatus for displaying an image on a screen. If the light axis of he projector is inclined with respect to the screen surface, the image displayed on the screen surface is distorted. In order that an undistorted image may be displayed on the screen surface even if the light axis is inclined with respect to the screen surface, a projector has a trapezoidal correction unit for correcting a distortion of the image, based on an inclination angle of the light axis with respect to the screen surface. Such a projector is disclosed in, for example, Unexamined Japanese Patent Application KOKAI Publication No. 2001-339671 on page 3 and in FIG. 1.
The trapezoidal correction unit of a conventional projector sets a quadrangle after trapezoidal correction within a quadrangle which is the projection frame before trapezoidal correction. The trapezoidal correction unit corrects an input image signal by projectively transforming the quadrangle before correction represented by the input image signal into the quadrangle after correction temporally continuously.
However, unless the position of the quadrangle after correction is appropriate with respect to a vertical line that passes the light axis point, it becomes necessary to change the inclination angles of the projector both in the vertical direction and in the horizontal direction, at the time of manually correcting the projection position of the projection image in a manner that the position irradiated by the projection light from the projector comes to a right position. Further, since the size of the quadrangle after correction is changed if the inclination angles are changed, it is necessary to adjust the inclination angles while also adjusting the size of the quadrangle after correction. Like this, conventional projectors have a problem that their operability when correcting the projection position of the projection image is poor.
The content of the above-described publication is incorporated herein.